Dietary fat has been associated with the pathogenesis of colorectal cancer in both epidemiologic and animal experimental studies. Both the amount and the type of fat consumed are important factors in this process. Many potential mechanisms for the effect of fat on the colonic mucosa have been proposed, but none have been proven. This study will determine the effect of short-term administration of a diet with a high proportion of several different fats on the turnover (the sum of cell duplication and cell death) of the colonic epithelial cells in human volunteers with different risk factors for colorectal cancer. In addition, the relationship between dietary fat intake and colonic mucosal production of various prostaglandins will be explored.